Structural frame capable of absorbing impact energy

ABSTRACT

A structural frame capable of absorbing impact energy comprises structural frame member of metallic material defining closed rectangular cross-section. Portion of each of the structural frame members is bent in the direction perpendicular to the longitudinal direction of the frame and energy absorption materials of metallic material with bowl-shaped projections are attached to those two opposing inner surfaces of the frame members which oppose in the direction of bending so that the bowl-shaped projection abut against each other. Upon collision, due to the resistance to plastic deformation of the bowl-shaped deformation the shape of the cross section of the structural frame may be maintained in its initial state and no abrupt decrease of blending moment takes place.

Suzuki et al.

[ Aug. 6 1974 I STRUCTURAL FRAME CAPABLE OF ABSORBING IMPACT ENERGY [75]Inventors: Ichiro Suzuki; Hiroyuki Watanabe,

both of Toyota, Japan [73] Assignee: Toyota Jidosha Kogyo KabushikiKaisha, Toyota-shi, Japan 22 Filed: 0.31, 1972 211 App]. N0. 302,549

[30] Foreign Application Priority Data Dec. 8, l971 Japan 46-99271 [52]US. Cl. 280/106 R, 52/731 [51] Int. Cl B6241 21/00 [58] Field of Search280/106 R, 106 R; 52/731, 52/99, 573

[56] References Cited UNITED STATES PATENTS 2,125,692 8/1938 Ragsdale52/731 2,257,666 9/1941 Almdale 280/106 R Primary Examiner-PhilipGoodman Attorney, Agent, or Firm-Stevens, Davis, Miller & Mosher [57]ABSTRACT A structural frame capable of absorbing impact energy comprisesstructural frame member of metallic material defining closed rectangularcross-section. Portion of each of the structural frame members is bentin the direction perpendicular to the longitudinal direction of theframe and energy absorption materials of metallic material withbowl-shaped projections are attached to those two opposing innersurfaces of the frame members which oppose in the direction of bendingso that the bowl-shaped projection abut against each other. Uponcollision, due to the resistance to plastic deformation of thebowl-shaped deformation the shape of the cross section of the structuralframe may be maintained in its initial state and no abrupt decrease ofblending moment takes place.

4 Claims, 10 Drawing Figures PATENTEB NIB 6W4 I 3; 827. 712

sum 1 or 3 PATENTEB SHEET 3 BF 3 FIGS (A) FIG. IO

The present invention relates to an improvement in structural frame suchas a side member of a frame for a car, and has its object to increaseabsorption efficiency of an impact energy upon collision or the like andto provide a small and light-weight structural frame while maintainingsufficient reliability and safety.

It has been suggested, in a structural frame such as a car frame or aside member, to flex a portion thereof to absorb impact energy. However,since such a frame has too rapid decrease of load for deformation strokeand low absorption efficiency for energy, the overall thickness of thestructural frame must be increased for compensation therefor, whichresults in unnecessarily large and heavy structure in order to achieverequisite energy absorption efficiency.

The present invention is intended to provide a novel and improvedstructural frame which overcomes the above short comings.

The present invention will now be described in connection with theaccompaning drawings in which:

FIG. 1 is a fragmentary plane view of a car frame in accordance with onepreferred embodiment of the present invention,

FIG. 2 is a perspective view of one form of energy absorbing material,

FIG. 3 is a plane view, partly broken away, of a structural frame curvedsection,

FIG. 4 is a front view, partly broken away, of the structure of FIG. 3,

FIG. 5 is a cross-sectional view taken on a line VV in FIG. 3,

FIG. 6 is a lateral cross-sectional view of a structural frame curvedsection having an energy absorbing material affired, in accordance withanother form of the present invention,

FIG. 7 is a perspective view of other form of energy absorbing material,

FIG. 8(A), (B) and (C) illustrate deformed conditions of the structuralframe of the present invention,

FIG. 9(A), (B) AND (C) illustrates deformed condition of a conventionalstructural frame, and

FIG. 10 shows characteristic curve of axial load of the structural frameversus stroke.

Referring to the drawings, FIG. 1 is a plane view showing a frontsection of structural frames 1 and 2, which form side members of a car,to which the present invention is applied. The structural frames 1 and 2made of steel defining closed rectangular shape in cross section, asshown in FIG. 5, are formed with curved sections 3 and 4, respectively,in the directions perpendicular to their respective longitudinaldirections. These sections serve as energy absorption sections.

Several pairs of energy absorption materials 5 and 6 are arranged in thecurved sections 3 and 4, as shown in FIGS. 2 through 5.

Each energy absorption material is made of steel or the like and has abowl shaped projection 7a at its bottom, as shown in FIG. 2, andmounting flanges 8 and 9 at opposite sides of an opening and is shapedsuch that it is accomodated in the structural frames 1 and 2.

As shown in FIGS. 1, 3 and 5, the energy absorption materials 5 and 6are attached to flanges 8 and 9, as

shown in FIG. 2, by means of welding or the like so that bowl-shapedprojections 7a and 7b abut against those two inner sides 10 and 11 ofthe inner sides of the structural frames 1 and 2 which oppose in thedirection of curvature.

While three pairs of energy absorption materials are shown in theillustrated embodiment it should be understood that the presentinvention is not limited to this. Also, while the energy absorptionmembers 5 and 6 are curved such that the flanges 12 and 13 between theflanges 8 and 9 are slightly spaced from the inner sides 10 and 11 ofthe structural frames 1 and 2, the present invention is not limited tosuch a particular structure.

FIG. 6 shows another embodiment of the energy absorption materials inwhich bowl-shaped projection of each energy absorption material is ofdual structure comprising an inner member 14 and an outer member 15.FIG. 7 shows other embodiment in which the bowlshaped projection 7ashown in FIG. 2 is replaced with a flat projection 16 in whichreinforcement grooves 17 and 18 are formed, and opposite sides of theflat projection 16 is formed into a box-like mount having sidewalls 19and 20, the bottom walls 21 and 22 thereof being adapted to be attachedto the inner surfaces of the structural frames.

The impact energy absorption action of the structural frames thusconstructed in accordance with the present invention is now described incomparison with a conventional structural frame. When the structuralframes are used as the side members constituting car frames, the curvedsection 3 is formed, as stated above, to assure strength rigidity duringrun and to absorb impact energy. The curved section 3 shares withbending moment corresponding to the amount of eccentricity (H) shown inFIG. 1. Upon collision this section is bent to absorb the impact energy.

In a conventional structural frame 23, as shown in FIG. 9(A), at theinitial stage of collision, that is, when an axial load (F) is applied,the structural frame 23 deforms as shown in FIG. 9(B) by 24, and theframe cross-section begins to collapse before full plastic collapse loadof the structural frame 23 is reached. As the structural frame furtherdeforms the shape of the cross section is substantially collapsed, asshown in FIG. 9(C), until it no longer sustains bending moment. Thus,the axial load versus stroke characteristic curve in this case has, asshown in FIG. 10 by double dotted line, a peak of the axial load (F) ata point 9(B) which corresponds to the status of FIG. 9(B), and rapidlydecreases thereafter, and at point 9(C) corresponding to the status ofFIG. 9(C) the stroke proceeds without substantial resistance.

On the contrary, in the structural frame 25 according to the presentinvention as shown in FIG. 8(A), at the time when the axial load (F) isapplied, the bowlshaped projections 28 and 29 of the paired energyabsorption materials 26 and 27 attached to the curved section areabutted against each other and begin plastic deformation. Due to theresistance to this plastic deformation the shape of the crosssection ofthe structural frame 25 is maintained substantially in its initial stateso that it may withstand the load until the full plastic collapse loadof the structural frame 25 is reached. When the stroke of the loadfurther increases, the plastic deformation of the energy absorptionmaterials 26 and 27 proceeds as shown in FIG. 8(C) and thecrosssectional shape of the structural frame 25 deforms depending uponthe amount of deformation so that no abrupt decrease of the bendingmoment takes place. Accordingly, in the axial load versus strokecharacteristic curve for this case, the axial load (F) does not fallafter passing through the point 8(B) corresponding to the status of FIG.8(B), as shown in FIG. 10 by a solid line, and reaches the point 8(C)corresponding to the status of FIG. 8(C) and does not exhibit Abruptdecrease even thereafter.

This fact demonstrates that the structural frame according to thepresent invention presents a desirable impact energy absorptioncharacteristic.

As has been illustrated and described, according to the presentinvention, the absorption efficiency of the impact energy upon collisioncan be increased and hence smaller and lighter structural frame may beprovided for absorbing a given impact energy. By suitably adjustingand/or selecting the plate thickness of the structural frame, the shapeof cross section, material, the amount of eccentricity of the curvedsection, or the shape of the energy absorption material, the thicknessand material thereof, the axial load or deceleration may be controlledto any desired value. Furthermore, since the structural frame providesabsorption and relaxiation of the impact energy which are necessary andsufficient for the structural frame, it assures the reliability and thesafety and also insures the safety of the passengers when it is appliedto a car frame or the like.

What is claimed is:

1. In a strengthening frame for automobiles, a strengthening framecapableof absorbing impact energy comprising a strengthening frame ofmetal having a closed cross-- section such as rectangular shape; aplurality of curved portions curved inwardly of the said strengtheningframe by the front and/or rear end of the said frame in its longitudinaldirection; and energy absorption members of metal, wherein the bottom isprojected in a bowl-shape and the side edge portions of the openingfunction as flanges for the mounting,

the bowl-shaped projections of the said energy absorption members beingattached to the inside of the said strengthening frames at their curvedportions adjacent and opposite to each other.

2. A structural frame capable of absorbing impact energy in accordancewith the claim 1 wherein the energy absorption material is a dualbowl-shaped projection consisting of an inner member and an outer memberand mounting flanges at its opposite sides of the openmg.

3. A structural frame capable of absorbing impact energy in accordancewith the claim 1 wherein the energy absorption material has a flatprojection at its bottom, reinforcement grooves being formed in saidflat projection, a box-like mount having side walls being formed onopposite sides of the flat projection, and a mounting bottom wall atopposite side ends of the opening.

4. A structural frame capable of absorbing impact energy comprisingstructural frame members made of metal defining closed rectangularcrosssection, a portion of each of said structural frame members beingbent in the direction perpendicular to the longitudinal direction of thestructural frame members, and energy absorption materials made of themetal having bowlshaped projections at its bottom and mounting flangesat its opposite sides of the opening to the projection which areattached to those two opposing inner surfaces of the structural framewhich oppose in the direction of bending whereby the bowl-shapedprojections may abut against each other.

1. In a strengthening frame for automobiles, a strengthening framecapable of absorbing impact energy comprising a strengthening frame ofmetal having a closed cross-section such as rectangular shape; aplurality of curved portions curved inwardly of the said strengtheningframe by the front and/or rear end of the said frame in its longitudinaldirection; and energy absorption members of metal, wherein the bottom isprojected in a bowl-shape and the side edge portions of the openingfunction as flanges for the mounting, the bowl-shaped projections of thesaid energy absorption members being attached to the inside of the saidstrengthening frames at their curved portions adjacent and opposite toeach other.
 2. A structural frame capable of absorbing impact energy inaccordance with the claim 1 wherein the energy absorption material is adual bowl-shaped projection consisting of an inner member and an outermember and mounting flanges at its opposite sides of the opening.
 3. Astructural frame capable of absorbing impact energy in accordance withthe claim 1 wherein the energy absorption material has a flat projectionat its bottom, reinforcement grooves being formed in said flatprojection, a box-like mount having side walls being formed on oppositesides of the flat projection, and a mounting bottom wall at oppositeside ends of the opening.
 4. A structural frame capable of absorbingimpact energy comprising structural frame members made of metal definingclosed rectangular cross-section, a portion of each of said structuralframe members being bent in the direction perpendicular to thelongitudinal direction of the structural frame members, and energyabsorption materials made of the metal having bowl-shaped projections atits bottom and mounting flanges at its opposite sides of the opening tothe projection which are attached to those two opposing inner surfacesof the structural frame which oppose in the direction of bending wherebythe bowl-shaped projections may abut against each other.